The invention relates to a mobile radio transmission system with radio base stations and mobile stations.
Mobile radio transmission systems for covering a rather large radio coverage area have been conceived as cellular radio networks for a long time. Each cell of such a radio network comprises at least one radio base station that maintains a radio connection to the mobile stations located in its radio cell. To make the frequency band available for the radio system accessible to the largest possible number of subscribers in the whole mobile radio communications system, great importance is attributed to the radio network planning.
Channel allocation in a mobile radio network is then a difficult problem of the radio network planning. So far this has been solved by making forecasts in the planning phase about the expected traffic density and radio wave propagation. Such calculations then result in numbers of channels necessary for each radio base station and corresponding compatibility requirements of the individual radio base stations. Via suitable computing methods it is then possible to generate channel lists i.e. lists of channels which are to be installed in the radio base stations concerned from these necessary numbers of channels. The disadvantage of such a procedure is that the correctness of the data on which the planning is based is to be trusted and the planning is to be repeated with each change of the network. Especially in the microcell area, this procedure of planning of radio networks is almost inapplicable because, on the one hand, microcells by nature require a degree of detail that can no longer be effectively calculated beforehand and, on the other hand, microcells in a city area are subjected to permanent changes. For example, the shadowing properties of buildings are no longer modelled stochastically as they have been thus far, but the necessary accuracy of the field strength propagation cannot be effectively calculated in advance. On the other hand, for example building sites and traffic jams represent continuous changes of the network. However, since microcells have the only possibility of coping with the present or future dramatic increase of radio subscribers, on the whole the procedure of preliminary planning no longer seems to be practical.
From EP 0 585 994 A2 is known a mobile radio transmission system of the type defined in the opening paragraph.